the right design, selection, and placement of guardrails reduces crash frequency and severity - guardrails aren't even installed unless hitting them will result in less severe damage than whatever is past them off the road, and when possible, a run off area is better than a guard rail for minimizing damage

“You don’t want to indiscriminately line roadways with guardrail,” says Roger Bligh, a civil engineer with TTI. “If there’s a reasonable runoff recovery area out there, then we want a driver to have that opportunity rather than striking a guardrail. We generally use a guardrail only when striking it is going to be less severe than striking another obstacle or hazard that might be on the roadside.”

https://www.caranddriver.com/news/a15359111/what-happens-if-you-crash-into-the-pointy-end-of-a-guardrail/
https://docplayer.net/23717004-2011-transportation-short-course-roger-bligh-ph-d-p-e-texas-transportation-institute.html